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 *   Copyright (c) 2022 Huawei Device Co., Ltd.
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import CharsetProber      from './CharsetProber';
import CodingStateMachine from './statemachine/CodingStateMachine';
import Constants          from '../Constants';
import {ProbingState}     from './CharsetProber';
import SMModel            from './statemachine/SMModel';
import UTF8SMModel        from './statemachine/UTF8SMModel';

class UTF8Prober extends CharsetProber {
  ////////////////////////////////////////////////////////////////
  // constants
  ////////////////////////////////////////////////////////////////
  public static ONE_CHAR_PROB:number = 0.5; //float

  ////////////////////////////////////////////////////////////////
  // fields
  ////////////////////////////////////////////////////////////////
  private codingSM:CodingStateMachine;
  private state:ProbingState;
  private numOfMBChar:number;
  private static smModel:SMModel = new UTF8SMModel();

  ////////////////////////////////////////////////////////////////
  // methods
  ////////////////////////////////////////////////////////////////
  public constructor() {
    super();
    this.numOfMBChar = 0;
    this.codingSM = new CodingStateMachine(UTF8Prober.smModel);

    this.reset();
  }

  public getCharSetName():string {
    return Constants.CHARSET_UTF_8;
  }

  public handleData(buf:ArrayBuffer, offset:number, length:number):ProbingState {
    let codingState:number;
    let maxPos = offset + length;

    let intArray = new Int8Array(buf);
    for (let i:number=offset; i<maxPos; ++i ) {
      codingState = this.codingSM.nextState(intArray[i]);
      if (codingState == SMModel.ERROR) {
        this.state = ProbingState.NOT_ME;
        break;
      }
      if (codingState == SMModel.ITSME) {
        this.state = ProbingState.FOUND_IT;
        break;
      }
      if (codingState == SMModel.START) {
        if (this.codingSM.getCurrentCharLen() >= 2) {
          ++this.numOfMBChar;
        }
      }
    }

    if (this.state == ProbingState.DETECTING) {
      if (this.getConfidence() > CharsetProber.SHORTCUT_THRESHOLD) {
        this.state = ProbingState.FOUND_IT;
      }
    }

    return this.state;
  }

  public getState():ProbingState {
    return this.state;
  }

  public reset():void {
    this.codingSM.reset();
    this.numOfMBChar = 0;
    this.state = ProbingState.DETECTING;
  }

  public getConfidence():number {
    let unlike:number = 0.99; // float

    if (this.numOfMBChar < 6) {
      for (let i:number=0; i<this.numOfMBChar; ++i) {
        unlike *= UTF8Prober.ONE_CHAR_PROB;
      }
      return (1.0 - unlike);
    } else {
      return 0.99;
    }
  }

  public setOption():void {
  }
}

export default UTF8Prober;